Nearly 400 million Facebook users will see the service's 'I'm a Voter' feature this year

Facebook's 'I'm a Voter' feature encouraged 340,000 Americans to vote in the 2010 election, a study found

By clicking 'Im a Voter,' Facebook users let their friends know they participated in their country's election

Hundreds of millions of Indians had their fingers inked blue to show they voted in recent nationwide elections. According to Facebook, 4 million of them clicked the “I’m a Voter” button to broadcast their participation on the social media network.

The feature was designed by the company to encourage people to prompt friends to vote. "There is a real social multiplier effect," Facebook spokesman Andy Stone told Reuters. "When people see on Facebook that their friends have voted, they themselves are motivated to vote." By clicking "I'm a Voter," users will be able to quickly share a post that will show up on their friends' News Feeds. (It does not reveal who or what they voted for.)

Facebook first introduced what it calls its voter megaphone during the 2008 U.S. presidential election. In the 2012 election, more than 9 million users took advantage of the feature.

Now it’s going international. Next up will be the European Parliament and Colombian elections, both this week. Users in South Korea, Indonesia, Sweden, Scotland, New Zealand and Brazil can use the feature later this year when their elections come around. The Menlo Park, Calif., social network said it would allow nearly 400 million users around the world to let friends know they voted in national elections.

And of course, American users well get the option to press the button as it gets closer to the 2014 midterm elections in November.

It’s not just social media fluff. A study published in Nature, a scientific journal, estimated that more than 340,000 voters turned out to cast their ballots during the 2010 midterm elections as a result of seeing their friends' "I'm a Voter" Facebook status.